Self-Consistent Magnetic Stellar Evolution Models of the Detached, Solar-Type Eclipsing Binary EF Aquarii

TL;DR

This paper presents a new stellar evolution model that incorporates magnetic fields, successfully explaining observed discrepancies in the properties of the binary system EF Aquarii by accounting for magnetic suppression of convection.

Contribution

The authors develop a self-consistent 1D stellar evolution code that includes magnetic effects, improving the modeling of magnetic activity's impact on stellar structure.

Findings

Magnetic fields can explain radius and temperature discrepancies in EF Aquarii.

Magnetic field strengths in models align with observational estimates from X-ray and Ca II K emissions.

Magnetic suppression of convection significantly alters stellar radii and temperatures.

Abstract

We introduce a new one-dimensional stellar evolution code, based on the existing Dartmouth code, that self-consistently accounts for the presence of a globally pervasive magnetic field. The methods involved in perturbing the equations of stellar structure, the equation of state, and the mixing-length theory of convection are presented and discussed. As a first test of the code's viability, stellar evolution models are computed for the components of a solar-type, detached eclipsing binary (DEB) system, EF Aquarii, shown to exhibit large disagreements with stellar models. The addition of the magnetic perturbation corrects the radius and effective temperature discrepancies observed in EF Aquarii. Furthermore, the required magnetic field strength at the model photosphere is within a factor of two of the magnetic field strengths estimated from the stellar X-ray luminosities measured by ROSAT and those predicted from Ca II K line core emission. These models provide firm evidence that the suppression of thermal convection arising from the presence of a magnetic field is sufficient to significantly alter the structure of solar-type stars, producing noticeably inflated radii and cooler effective temperatures. The inclusion of magnetic effects within a stellar evolution model has a wide range of applications, from DEBs and exoplanet host stars to the donor stars of cataclysmic variables.